But the "Dwarf Toy", (I forget which one) and some of the others turned out to be needed for Requisition Quests late in the game.
At over 250 hours invested, they were one of the reasons I gave up on being a "Completionist" on my first playthrough. 
I'd keep dwarf stuff found in the Hissing Wastes, but I wouldn't be hoarding the stuff the entire game just so you can finish that requisition once you finally get there.
Due to bugs, you can never be "completionist" anyway, and the chances of getting close the first time through seem small (you need to plan how you handle requisitions since a lot of the components are dependent on enemies that can stop spawning).
If you don't find yourself limited by the storage capacity when exploring big areas, then feel free to hang on to more of the valuables, but the list here should be fairly complete (there's also an Orders item that you can find in the Hinterlands that apparently works in a requisition in the Graves, but I haven't seen that one yet).